Study on the properties of bauxite modified by acid leaching and calcination for improving fluorine removal

Abstract

In order to improve the fluorine removal performance of bauxite, the effects of different calcination temperatures and several acids (HCl, H 2 SO 4 , H 2 C 2 O 4 ) on the fluorine removal performance of bauxite were investigated. It was found that the calcination temperature of 500 C and the modification of H 2 SO 4 had the best fluorine removal performance. Under the same experimental conditions, the fluoride removal rate of the modified bauxite could reach 99.54%, which was much higher than that of unmodified bauxite (52.69%). The adsorbent was characterized by XRD, FTIR, BET, TG/DSC, and XRF. The influence of the addition amount of adsorbent, initial concentration of fluorine, adsorption time, and temperature on fluorine removal performance was studied. The adsorption process reached equilibrium in 32 min, and the inhibition order of coexisting anions was H 2 PO 4 À < HCO 3 À < CO 3 2À < Cl À . The pseudo-secondorder kinetic model was more suitable for the fluoride removal process of modified bauxite. Thermal regeneration had better regeneration performance than alkali leaching regeneration.